Figure 8. Analysis of errors in letter identification experiment.

Table 1. Percentage of correct identifications as a function of the number of dots in a letter. Note that of the 26 letters of the alphabet, a single letter has 1 dot, five letters have 2 dots, nine letters have 3 or 4 dots and five letters have 5 dots.
number of dots in letter legibility
1 66.7%
2 63.6%
3 60.2%
4 51.5%
5 43.3%

Table 2. Distribution of incorrect letter identifications as a function of the number of dots incorrectly identified. The second column shows the distribution that would result from random answers while the third shows the distribution obtained in the experiment. For example, 48.1% of the errors consisted in a single incorrect dot while that proportion should be 15.7% if answering randomly.
number of erroneous dots probability experiment
1 15.7% 48.1%
2 28.6% 23.8%
3 29.5% 17.1%
4 18.8% 8.0%
5 6.5% 2.8%
6 0.9% 0.2%